Abstract: A transistor voltage-controlled oscillator (VCO) and a frequency synthesizer having the transistor VCO are provided. The frequency synthesizer adopts a divide-by-five injection-locked frequency divider, which includes a five-stage inverter ring oscillating frequency dividing circuit for reducing the operating frequency of the oscillating signal from the VCO, thus decreasing power consumption due to counting operation of the frequency synthesizer. The transistor VCO includes three transistor switching capacitor sets connected in parallel to one another to form a parallel structure. The gates of the transistor switching capacitor sets are connected to respective operating voltage sources, so as to switch the status of the corresponding transistor switching capacitor set, which in turn adjusts the harmonic frequency generated by the VCO, thereby allowing the VCO to generate a corresponding operating frequency with enough bandwidth.

Abstract: A FET transistor voltage-controlled oscillator is provided that includes a crossed-coupled inductor capacitor tank (LC-Tank) transistor voltage-controlled circuit having a first transistor and a second transistor, as well as a transistor frequency multiplying circuit having a third transistor and a fourth transistor. In the design, the gate of the first transistor is connected to the drain of the second transistor, and the gate of the second transistor is connected to the drain of the first transistor. Then, the source of the third transistor is connected to the source of the first transistor, and the source of the fourth transistor is connected to the source of the second transistor. Last, the gate of the third transistor is connected to the gate of the fourth transistor, and the drain of the third transistor is connected to the drain of the fourth transistor.